In conventional piston engines, the four strokes: intake, compression, power and exhaust are carried out in the same cylinder. There is a large amount of thermal energy taken away by the waste gases as high-temperature and high-pressure burning gases can not expand sufficiently in the power stroke. However, while the power acting on the top of the piston is transmitted through the piston and connecting rod, and the crankshaft, there are losses in component forces. The engine also needs exhaust valves that are in very adverse working circumstances and very difficult to cool down. They are also liable to erosion and have a short life. In addition, the driving of valves consumes engine power, and creates noise. Furthermore, there are the inertia losses as the valves and pistons are reciprocating. These inertia losses are increased with the increase of the speed of the engine and also severely affect the acceleration character and top velocity of the engine, making the engine unbalanced. Also, restricted by structure and operation principles, the air-fuel mixture is incomplete, burning time is short, and combustion is not complete. Consequently, fuel consumption is high and efficiency is low, with serious emission pollution and high noise level. What is more, with its large volume, heavy weight, complicated structure, large number of parts, high requirement for manufactured technology, high cost, and high fault rate, it is difficult to meet the modern requirements of transports and communications.
With its small volume, light weight, little inertia loss, reduced vibration and fewer moving parts, the rotary engine has been proposed as a viable alternative to the conventional piston engine. A successful example is known as the "Wankel Rotary Engine" built by the German engineer Felix Wankel in the 1950s. However, the combustion in this is far from complete, so it consumes a lot of oil, and produces heavy emission pollution.
Another type of rotary engine is the vane rotary engine, for example, in China patent application No. 91102310.0 (Published No. CN1055410A). The patent discloses an external combustion engine having the radial vane pistons. The housing, rotor and main shaft have been placed on a same axis, so the main shaft does not suffer the shearing stress as the rotor does not work in the side press situation. The process of intake-compression phase and expansion-exhaust phase is completed by taking concerted action between the rotor and the intake-compression chamber and expansion-exhaust chamber. There are two combustion chambers between the intake-compression chambers and expansion-exhaust chambers, and those chambers have been connected by a number of components such as air pipes, check valves, compressed gas pipes, gas store cells and injectors. However, the configuration is more complicated, and there a large amount of thermal losses and pressure drops while gases are moving through those pipes, valves and injectors. Also, the burning time can not be controlled efficiently, and burning efficiency is unsatisfactory. So this type of engine is far from utilization.
Other related vane rotary engines have been developed as seen, for example, in U.S. Pat. No. 5,277,158. This patent however discloses a multiple vane rotary internal combustion engine. The housing and the portion of the rotor between the adjacent vanes form the working chamber, and so the working procedure of the engine is completed within. It could be to use variety grades of petrol fuels without modifications. The wearing rate and thermal releasing area in this engine are large because of many vanes.